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Import SortLimitBug dump in a new database.

Run following aggregation and check Id of last record return (67)

db.SortLimitBug.aggregate(( [ { "$project" : { "TM30" : 1, "OM30":1} }, { "$sort" : { "TM30" : NumberInt(-1) } }, { "$match" : { "OM30" : { "$lt" : 5.0 } } }, { "$skip" : NumberInt(0) }, { "$limit" : NumberInt(25) } ]))

Run second page: Check Id of first record: is 67 instead of 72

db.SortLimitBug.aggregate(( [ { "$project" : { "TM30" : 1, "OM30":1} }, { "$sort" : { "TM30" : NumberInt(-1) } }, { "$match" : { "OM30" : { "$lt" : 5.0 } } }, { "$skip" : NumberInt(25) }, { "$limit" : NumberInt(25) } ]))

Run same queries without $limit and records will be correct
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Import SortLimitBug dump in a new database. Run following aggregation and check Id of last record return (67) db.SortLimitBug.aggregate(( [ { "$project" : { "TM30" : 1, "OM30" :1} }, { "$sort" : { "TM30" : NumberInt(-1) } }, { "$match" : { "OM30" : { "$lt" : 5.0 } } }, { "$skip" : NumberInt(0) }, { "$limit" : NumberInt(25) } ])) Run second page: Check Id of first record: is 67 instead of 72 db.SortLimitBug.aggregate(( [ { "$project" : { "TM30" : 1, "OM30" :1} }, { "$sort" : { "TM30" : NumberInt(-1) } }, { "$match" : { "OM30" : { "$lt" : 5.0 } } }, { "$skip" : NumberInt(25) }, { "$limit" : NumberInt(25) } ])) Run same queries without $limit and records will be correct

We have discovered an issue that we think related to the $sort + $limit optimizer.
We have attached dump of a sample collection.

Second query with a limit of 25 has as first element the last element of the first page (25th) instead of the 26th correct one.

Same queries performed without limit works properly.

duplicates

SERVER-28195 $skip followed by $limit in aggregation resort & lost records when $sort by equal values